Sinn Féin leader Gerry Adams said he is predicting a “step change” away from the “two-and-a-half party” political system which he claims has served the country badly.

Speaking after an opinion poll showed his party is poised to win seats in all three constituencies in next month’s European elections, with two of its candidates topping the polls, Mr Adams said voters are “responding in greater numbers” to the party’s “message of hope and change”.

Addressing the campaign launch of Lynn Boylan — who is top of the opinion poll in the Dublin constituency with 20% support — Mr Adams said his party’s message was that “things do not have to be the way they are, there is a better way”.

He said: “Sinn Féin MEPs will not be ‘yes men’ or ‘yes women’ in the EU. We have had enough of that. They will be Irish representatives in the EU, not EU representatives in Ireland.”

The Labour Party — which could be left without a single seat in the European Parliament, according to the opinion poll — has warned of the dangers of such an approach.

West Cork TD Michael McCarthy said people should think “long and hard” about the implications of electing Sinn Féin MEPs.

“Relationships in Europe are very important and if we return three anti-Europe MEPs, it sends out a very serious signal to our colleagues in Europe and could cause serious difficulties for the Irish recovery,” Mr McCarthy said.

He said Sinn Féin MEPs would not be part of any significant grouping in the European Parliament. “They are the masters of fairytale economics and the stakes are too high at this point of our recovery,” he said.

Fianna Fáil leader Micheál Martin said Sinn Féin has adopted the same approach to opposition as Labour did in the past: “They attack everything and pretend that there are no choices to be made — everyone can and should have what they want.”

He said Fianna Fáil “reject this approach” which “offered the country nothing in the past and offers nothing today”.

Sinn Féin had 10% of support at the 2011 general election and has increased this to 21% in the latest Red C monthly tracking poll.

Surveys by Millward Brown in the Sunday Independent found it is likely to win a seat in each of the three constituencies of the European elections, possibly topping the poll in the Midlands, North, West area with Matt Carthy.

Its candidate in Ireland South, — which covers Munster and Leinster — Liadh Ní Riada, is also polling well with 15% of support of 507 adults surveyed in the area.